Polymer Dispersed Liquid Crystal Photovoltaic Device and Method for Making

ABSTRACT

A novel photovoltaic device including a polymer dispersed liquid crystal (PDLC) material that is capable of converting solar energy to electrical energy and method for making. The device may optionally include a conductive container for holding the PDLC material. In an exemplary embodiment, the invention is directed to a self assembled PDLC material, a holographically synthesized PDLC material or a block co-polymer dispersed liquid crystal material. It is envisioned that the invention may be used a power source for any device, system or application. In particular, the invention may be used for any application involving the conversion of solar energy to electrical energy.

RELATED APPLICATION DATA

This application is a divisional of U.S. patent application Ser. No.13/123,977, filed Apr. 13, 2011, which claims priority to InternationalApplication No. PCT/US09/060617, filed Oct. 14, 2009, and U.S.Provisional Application No. 61/105,275, filed Oct. 14, 2008, the entiredisclosure of which is hereby incorporated by reference as if set forthfully herein.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention is directed to polymer dispersed liquid crystalphotovoltaic devices. It is envisioned that the invention may be used toconvert solar energy to electrical energy.

2. Brief Description of the Prior Art

In spite of the widely appreciated magnitude of what has come to becalled the energy crisis, there are still critical gaps in many methodscurrently available for energy generation. Specifically, despite recentadvances in the field of renewable solar energy, current state of theart solar cells are inefficient, expensive and are limited in theirapplication.

Recently, much attention has been directed towards the development oforganic solar energy devices. Carbon nano-tubes (See Michael W. Rowell,et al., “Organic Solar Cells With Carbon Nanotube Network Electrodes,”Applied Physics Letters, vol. 88, pgs. 233506-1-233506-3 (2006); RossUlbricht, et al., “Transparent Carbon Nanotube Sheets as 3-D ChargeCollectors in Organic Solar Cells,” Solar Energy Materials & SolarCells, vol. 91, pgs. 416-419 (2007)), electrically conductive polymers(See G. Li, et al., “Efficient Inverted Polymer Solar Cells,” AppliedPhysics Letters, vol. 88, pgs. 253503-1-253503-3 (2006); Gavin A.Buxton, et al., “Computer Simulation of Polymer Solar Cells,” ModelingSimul. Mater. Sci. Eng., vol. 15, pgs. 13-26 (2007), published online onDec. 12, 2006) and various types of liquid crystals (See MiguelCarrasco-Orozco, et. al., “New Photovoltaic Concept: Liquid-CrystalSolar Cells Using a Nematic Gel Template,” Advanced Materials, vol. 18,pgs 1754-1758 (2006); Sandeep Kumar, “Discotic Liquid Crystals For SolarCells,” Current Science, vol. 82, no. 3 pgs. 256-257 (2002)) have beeninvestigated in an attempt to overcome the problems of the prior art.Although such organic solar energy devices have yielded higher quantumefficiencies, they have a lower overall power output than currentsilicon based solar cell designs.

The possible use of polymer dispersed liquid crystals (PDLCs) in solarenergy devices has raised some interest because PDLCs areenvironmentally friendly, relatively inexpensive to manufacture and haverelatively high energy conversion efficiency in comparison toconventional silicon solar cells. Nematic and chiral nematic liquidcrystals, in particular, have been previously investigated. While theseliquid crystals work well for optical applications, their relativelysmall molecular structures and lack of conjugated rings make themminimally photovoltaic and therefore not ideal for solar cellapplications.

Additionally, PDLCs which have been incorporated in solar energygeneration systems are structurally incapable of solar energyconversion. Rather these PDLCs are typically coupled to a conventionalsolar cell and function to focus light towards the solar cell. Forexample, U.S. Pat. No. 7,206,044 (hereinafter “Li”) discloses a solarcell in combination with a liquid crystal display. The liquid crystaldisplay includes a cholesteric liquid crystal or polymer dispersedliquid crystal placed between opposing transparent plates (See col. 2,lines 11-17 of Li). A conventional solar cell is joined to one side ofthe liquid crystal display with a coupling layer such as a transparentadhesive material (See col. 2, lines 34-39 of Li).

U.S. Pat. No. 7,226,966 (hereinafter “Kambe”) discloses a compositematerial comprising polymers and inorganic particles for use infabricating optical and electro-optical materials, optical devices andintegrated optical circuits (See col. 4, lines 38-47 of Kambe). Kambementions the possibility of, but does not describe, a PDLC photovoltaicdevice. Rather, Kambe discloses that the composite material may includea polymer-dispersed liquid crystal display (See col. 30, lines 12-19 ofKambe) and self-assembling block copolymers (See col. 14, lines 17-23,52-59 of Kambe) and that photonic crystals may possibly be used in theformation of solar cells (See col. 38, lines 27-33 of Kambe).

These patents, therefore, do not effectively disclose a PDLC materialthat functions as a solar cell. In general, the PDLCs used in prior artsystems incorporate liquid crystals which filter light rather thanabsorb light and the polymer matrix is typically insulating rather thanconducting.

Therefore, there exists a need to develop a PDLC that is capable ofefficiently converting solar energy to electrical energy.

SUMMARY OF THE INVENTION

The invention is directed to embodiments of photovoltaic devices thatinclude a polymer dispersed liquid crystal material, having a conductivepolymer and light absorbing liquid crystals and an electric lead fortransmitting electrical energy generated by the photovoltaic devices.

In another embodiment, the photovoltaic device includes a photo-curablepolymer dispersed liquid crystal material having a conductive polymerand a liquid crystal. The photovoltaic device also includes an electriclead and, optionally, a container for retaining said polymer dispersedliquid crystal material, wherein the container includes electricallyconductive elements.

The present invention is also directed to a novel method for fabricatinga photovoltaic device including the steps of synthesizing a polymerdispersed liquid crystal material having a conductive polymer and lightabsorbing liquid crystals, wherein the polymer dispersed liquid crystalmaterial is capable of converting solar energy to electrical energy. Themethod further includes the step of incorporating an electrical lead.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of one embodiment of a self-assembling PDLCmaterial.

FIG. 2( a) is a perspective view of one embodiment of an H-PDLCmaterial.

FIG. 2( b) is a SEM scan of one embodiment of an H-PDLC material.

FIG. 3( a) is a perspective view of one embodiment of a block co-polymerdispersed liquid crystal material.

FIG. 3( b) is a perspective view of a block co-polymer wire.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

For illustrative purposes, the principles of the present invention aredescribed by referencing various exemplary embodiments thereof. Althoughcertain embodiments of the invention are specifically described herein,one of ordinary skill in the art will readily recognize that the sameprinciples are equally applicable to, and can be employed in otherapparatuses and methods. Before explaining the disclosed embodiments ofthe present invention in detail, it is to be understood that theinvention is not limited in its application to the details of anyparticular embodiment shown. The terminology used herein is for thepurpose of description and not of limitation. Further, although certainmethods are described with reference to certain steps that are presentedherein in certain order, in many instances, these steps may be performedin any order as may be appreciated by one skilled in the art, and themethods are not limited to the particular arrangement of steps disclosedherein.

For purposes of the present invention, “container” may refer to achamber defined by at least two sides, wherein the chamber may have anydepth, width, height, shape or configuration suitable for retaining apolymer dispersed liquid crystal layer.

It must be noted that as used herein and in the appended claims, thesingular forms “a”, “an”, and “the” include plural references unless thecontext clearly dictates otherwise. Thus, for example, reference to “apolymer” includes a plurality of polymers and equivalents thereof knownto those skilled in the art, and so forth. As well, the terms “a” (or“an”), “one or more” and “at least one” can be used interchangeablyherein. It is also to be noted that the terms “comprising”, “including”,and “having” can be used interchangeably.

The present invention is directed to a novel polymer dispersed liquidcrystal (PDLC) photovoltaic device and a method for making the device.The PDLC photovoltaic device includes a PDLC material 1 that convertssolar energy to electricity. PDLC material 1 may be synthesized from aconductive polymer 2 and photosensitive liquid crystals 3. Morespecifically, liquid crystals 3 absorb light, convert photons toelectrons and induce an electron flow in conductive polymer 2. Theresulting electrical current is then carried across the conductivepolymer 2, and electrical leads 7 operatively associated with theconductive polymer 2 transport the current to an energy storage deviceor to an electrical device for immediate use. Consequently, PDLCmaterial 1 is capable of converting solar energy to electricity withoutthe assistance of conventional photovoltaic devices. It is envisionedthat the present invention may be useful for any application involvingor any device/system capable of being powered by a solar energy source.

Polymer 2 may include any conductive polymer. Preferably, polymer 2 ismiscible with liquid crystal 3. One way to enhance polymer miscibilityis to employ water-based polymers. Preferably, polymer 2 may also havehigh transparency to visible or ultraviolet light and is preferablyphoto-curable. Photo-curing may be carried out using, for example,ultraviolet, visible or infrared light. In an exemplary embodiment,polymer 2 may include, but is not limited to, highly conductive organicpolymers such as Poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate)(PEDOT:PSS), polyaniline or combinations thereof. In general, variouspolythiophenes, pyrazoloquinolines, polysilanes and carbon black dopedultra-high molecular weight polyethylenes may be employed in the presentinvention. Preferred characteristics of these materials are a sheetresistance of less than 1000 ohm/square and a bulk conductivity ofgreater than 500 S/cm.

Polymer 2 may further include at least one pair of electricallyconductive elements 4 for inducing and directing an electric currentthrough polymer 2. Conductive elements 4 may be any material capable of,and may have any shape or configuration suitable for conducting anelectrical charge. In an exemplary embodiment, conductive elements 4 maybe electrodes fabricated from metallic compounds. More preferably, theelectrodes are fabricated from different metallic compounds to enable awork function difference and induce a directional current. Mostpreferably, the electrodes are metallic nanoparticles. Suitablematerials include, but are not limited to, silver, indium, tin, tinoxide, zinc, zinc oxide, silicon, lead and copper.

Liquid crystals 3 of PDLC material 1 may include any material that iscapable of absorbing photons, exciting electrons and is miscible withpolymer 2. Preferably, the molecular structure and molecular orientationof liquid crystals 3 are adapted to efficiently and effectively absorblight, e.g. have a high photovoltaic activity. For example, liquidcrystals 3 may have conjugated ring structures, high charge mobilityand/or small bandgaps. The liquid crystal may be in any suitable phase,but is typically in an ordered phase rather than an isotropic phase. Theliquid crystal material may optionally be functionalized with one ormore functionalities to vary the properties of the material as discussedin greater detail below.

The system of the present invention will have both holes and electrons.Thus, exciton (a paired electron and hole) mobility is an importantaspect of the materials of the present invention. Suitable liquidcrystal materials will exhibit photovoltaic activity when exposed to oneor more of visible, near infrared or ultraviolet radiation and aremiscible in the polymer matrix material. Preferred liquid crystalmaterials are also thermally stable, non-isotropic at ambienttemperatures (5-40° C.), metallically doped and have a large core ringstructure.

Liquid crystals 3 may be any suitable photovoltaic liquid crystal. In anexemplary embodiment, liquid crystals 3 may be discotic liquid crystals,nematic liquid crystals, chiral nematic liquid crystals or a combinationthereof. Preferably, liquid crystal 3 is a discotic liquid crystal whichmay be formed into a columnar array as shown. In one preferredembodiment, liquid crystal 3 may be a silver-complexed, large ringstructure phthalocyanine, hexabenzocoronene, various oxytriphenylenesand hexatrioxaocytylthiophenylene (TP6EO2M).

Exemplary embodiments of the discotic liquid crystals are described inL. Schmidt-Mende, et al., “Self-Organized Discotic Liquid Crystals forHigh-Efficiency Organic Photovoltaics,” Science, vol. 293, pgs.1119-1122 (Aug. 10, 2001); K. Scott, et al., “Quantum efficiency ofphotogeneration in discotic liquid crystals: Part 1: Temperature andwavelength dependence,” Molecular Crystals and Liquid Crystals Scienceand Technology, vol. 397, pgs. 253-261 (2003); K. Scott, et al.,“Quantum efficiency of photogeneration in discotic liquid crystals: Part2: Electric field and temperature dependence,” Molecular Crystals andLiquid Crystals Science and Technology, vol. 397, pgs. 263-271 (2003);Richard J. Bushby, et al., “Photoconducting liquid crystals,” CurrentOpinion in Solid State and Material Science, vol. 6, pgs. 569-578(2002); K. J. Donovan, et al., “Molecular Engineering the PhototransportProperties of Discotic Liquid Crystals,” Molecular Crystals and LiquidCrystals Science and Technology, vol. 396, pgs. 91-112 (2003); loanParaschiv, “H-Bond Stabilized Columnar Discotic Liquid Crystals,” Ph.D.Thesis Wageningen University, (Jan. 19, 2007); S. Laschat, et al.,“Discotic Liquid Crystals: From Tailor-Made Synthesis to PlasticElectronics,” Angewandte Chemie International Edition, vol. 46, pgs4832-4887 (2007); A. Rybak, et al., “Charge carrier transport in layersof discotic liquid crystals as studied by transient photocurrents,”Synthetic Metals, vol. 156, pgs. 302-309 (2006); K. Yoshino, et al.,“Novel Electrical and Optical Properties of Discotic Liquid Crystals,Substituted Phthalocyanine Rare-Earth Metal Complexes,” Proceedings of13^(th) International Conference on Dielectric Liquids (ICDL '99) Nara,Japan, July 20-25, pgs. 598-601 (1999); Xiaoli Zhou, et al., “NatureInspired Well-Defined Discotic Liquid Crystal Porphyyrins for OrganicPhotovoltaics: New Opportunity and New Challenge,” Colorado RenewableEnergy Collaboratory Poster Abstracts for the Workshop on EfficientConservation of Solar Energy to Electricity and Fuel Cells, poster 35http://www.coloradocollaboratory.org/crsp_abstracts.html (viewed Oct.13, 2006); Marcel Kastler, “Discotic Materials for Organic Electronics,”Ph.D. Thesis in the department of Chemistry, Pharmacy and Geosciences atJohannes Gutenberg-Universitat Mainz (2006), the entire disclosures ofwhich are incorporated by reference herein.

Without wishing to be bound by theory, discotic liquid crystals have amolecular structure and molecular orientation that enables conductivity.The aforementioned exemplary liquid crystals may also be combined withnematic and/or chiral nematic liquid crystals.

Optimal ratios of the amount of liquid crystal 3 and polymer material 2will depend on the desire system properties. The range of applicableratios is from about 20:80 to 75:25 (liquid crystal to polymer).

Liquid crystals 3 may further be functionalized or include dopants toenhance one or more of conduction, polymer miscibility and excitontravel. For example, functionalization of the liquid crystal materialmay be used to alter the miscibility of the liquid crystal material withthe polymer and/or tune the work function of the liquid crystal materialto control the band gap. For good miscibility, a log P_(ow) close tozero would be desirable. For example, to improve polymer miscibility,the liquid crystal material may be functionalized with hydrophilicgroups. Band gaps comparable to those of conventional siliconsemiconductor materials, e.g. about 1.4 eV are desirable. In exemplaryembodiments, the functional group may be metallic cross-linkingcompounds, silica, hydroxyl groups, carbon nanotubes, grapheme, carbonblack and metallic nanoparticles such as those described above, or anycombination thereof.

PDLC material 1 fabricated from polymer 2 and liquid crystals 3,discussed above, may have material characteristics desirable forenabling solar energy conversion, as well as properties enabling use ofthe PDLC material 1 in a wide variety of applications. In an exemplaryembodiment, PDLC material 1 may have any geometric configuration andmaterial properties suitable for solar energy conversion. PDLC material1 may be fabricated to have any desired thickness. In an exemplaryembodiment, PDLC material 1 may have a thickness of up to 2.5 cm. In analternative exemplary embodiment, PDLC material 1 may have a thicknessof less than about 10 millionths of a meter. Preferred ranges for thinfilm PDLC materials are from 0.5-50 μm, while thicknesses of suitableself-assembling paint materials will typically be up to 2 mm thick. Thethickness of PDLC material 1 may be customized to suit the applicationfor which it is to be used. In an exemplary embodiment, PDLC material 1is a liquid that conforms to the shape and configuration of itscontainer and may polymerize or cure upon exposure to sunlight,controlled levels of electromagnetic radiation, heat, pressure,catalyzed with, for example, acid/base or metal, or a combinationthereof. Because PDLC material 1 is capable of adapting its shape uponpolymerization, it may be customized for a wide variety of applications.

In an exemplary embodiment, PDLC material 1 may also be efficient inconverting solar energy to electrical energy and/or capable of producinga high electrical current output. The morphological structure of thepolymer/liquid crystal blends of PDLC material 1 enables effectiveenergy conversion within liquid crystals which are physically orientedwithin electron carrying polymeric matrices. By taking advantage of thephotovoltaic properties of the liquid crystals and the inherentlyconductive polymers, it is possible to synthesize a high efficiency PDLCmaterial 1. In an exemplary embodiment, PDLC material 1 may have anoverall energy conversion efficiency that is greater than about 3%, morepreferably, greater than about 7% and most preferably, greater than 15%.

In various embodiments, PDLC material 1 may also be opticallytransparent, flexible, durable, environmentally friendly or acombination thereof. These material properties further enable PDLCmaterial 1 to be adapted to a wide variety of applications. The PDLCmaterial should allow light penetration of visible, near infrared and/orultraviolet radiation of sufficient magnitude to allow a sufficientamount of the radiation to impinge on the liquid crystals 3 to providereasonable electrical energy generation. Also, it is desirable to have arelatively large surface area of contact between liquid crystals 3 andpolymer matrix 2 in order to enhance electrical conduction from liquidcrystals 3 to polymer matrix 2.

Optionally, the PDLC material 1 may placed or retained in a container 5.Container 5 may include electrically conductive elements 6, which mayhave any geometric configuration and may be fabricated from any materialsuitable for conducting an electric charge generated by PDLC material 1.In an exemplary embodiment, container 5 may be optically transparent,flexible, durable, environmentally friendly or a combination thereof. Inan exemplary embodiment, container 5 may be two pieces of transparentconducting glass located on either side of PDLC material 1. Morepreferably, at least one side of a glass surface may be reflective toreflect light towards PDLC material 1. Container 5 may be used, forexample, as part of a self-assembly process for self-assembling PDLCmaterial in situ in container 5. In such case, container 5 may definethe shape of the self-assembled PDLC material.

PDLC material 1 may be vacuum-filled into an evenly spaced cell orformed between two indium tin oxide (ITO) coated glass slides spacedapart from one another by a functionally suitable distance.Alternatively, PDLC material may be spin coated onto a substrate inmultiple layers.

At least one electrical lead 7 may be operatively associated withconductive elements 6 of container 5, conductive elements 4 of PDLCmaterial 1 or a combination thereof in order to direct the generatedelectrical current to an energy storage device, such as a battery orcapacitor, or to a device or system which is to be powered by theelectrical current.

In an exemplary embodiment, PDLC material 1 of the present invention maybe a self-assembled PDLC material, a holographically synthesized PDLC(H-PDLC) material or a block co-polymer dispersed liquid crystal (BCP)material.

Self-assembled PDLC materials may automatically organize one or both ofliquid crystals 3 and conductive elements 4 with polymer matrix 2 duringself-assembly. Upon exposure to sunlight, controlled levels of UVradiation, heat, pressure, and/or catalysts, for example, acid/base ormetal, or a combination thereof, polymerization and self-assembly isinitiated. During this process, liquid crystals 3 are dispersed asdroplets throughout polymer matrix 2 in a random manner and conductiveelements 4 may optionally be automatically positioned within polymermatrix 2 so as to conduct a charge across polymer matrix 2.Alternatively, conductive elements 4 may be separately placed in whichcase only the PDLC is self-assembled. Conductive elements 4 can beself-assembled, for example, by addition of silver nanoparticles and anaqueous silver complex having a lower density than the liquid precursormaterial such that the silver nanoparticles will sink to the bottom andform an electrode there, whereas the aqueous silver complex may float tothe top and form a second electrode there. This also provides a workfunction differential between the two electrodes to improve theconduction of electricity in the apparatus. Other combinations ofsuitable electrode materials may also be self-assembled in this manner.Conductive elements 4 may be positioned anywhere within PDLC material 1.For example, conductive elements 4 may be positioned within or in directcontact polymer 2, liquid crystals 3 or a combination thereof. Toenhance the conduction efficiency of PDLC material 1, in an exemplaryembodiment, conductive elements 4 may be positioned within or in directcontact with liquid crystals 3.

Once polymerized, the device may be capable of supplying electricalpower to any connected device. In addition to enabling self-assembly andminimizing manufacturing costs, this novel embodiment is unique in thatit may be photo-curable to assume any shape or configuration.Furthermore, the self-assembled PDLC may be optically transparent,highly flexible and may form passively in sunlight. These propertiesmake the self-assembled PDLC useful for a wide variety of applications,including, for example, as a paint or coating material which can beapplied to an existing substrate.

In an exemplary embodiment, the self-assembled PDLC material may besynthesized from a homogenous mixture of monomers, liquid crystals 3,photoinitators, and conductive elements 4, such as metallicnanoparticles and water complexed metallic nanoparticles. This mixturemay be poured into and subsequently conform to the shape of a container5 upon polymerization. Upon exposure to suitable polymerizationconditions, such as exposure to sunlight or controlled levels of UVradiation of about 20-220 mW/cm², more preferably, 90-120 mW/cm², and,most preferably, 100 mW/cm², the monomers react and self-assemble toform a polymeric matrix 2. Liquid crystals 3 diffuse into a normaldistribution of droplets throughout the cross-linked polymer matrix 2,as shown in FIG. 1.

Conductive elements 4 also automatically self-assemble from the metallicnanoparticles and water complexed metallic nanoparticles duringpolymerization. For example, metallic nanoparticles, which have a higherdensity and/or lower solubility than the water complexed metallicparticles, will settle on the bottom of the polymer solution due togravitational forces. Aqueous complexed metallic particles, having a lowdensity and high polarity, will phase separate to the top of the polymersolution. The inherent work function difference between the top andbottom of the polymer solution will induce a downward electric current,thereby enabling the conduction of an electrical charge from one portionof the PDLC matrix to another portion of the PDLC matrix.

In an alternative embodiment, PDLC material 1 may be holographicallyfabricated wherein polymer 2 and liquid crystals 3 are exposed to aholographic pattern, i.e. interference pattern, during synthesis. Asshown in FIG. 2( a), holographic patterning causes liquid crystals 2 toorganize during polymerization within polymer 2 in accordance with adesignated pattern. The patterning may be used to create layered liquidcrystal structures that increase overall solar energy conversionefficiency and current output. FIG. 2( b) is an SEM image of themorphology of an H-PDLC, showing that the synthesis process causespolymer 2 to cure in the bright fringes of the interference pattern,while liquid crystals 3 diffuse to the darker regions of theinterference pattern. In this embodiment, a grating structure is createdin the H-PDLC which provides efficient electron pathways within thematerial. Different H-PDLC morphologies may be achieved depending uponthe applied interference pattern. Conductive elements 4 may be added tothe H-PDLC system to induce a directional electric current.

The H-PDLC embodiment is advantageous because of its enhanced energyconversion efficiency and high current output. Additionally, this methodfor synthesizing H-PDLC may enable the production of structures whichare thin, flexible, stackable or combinations thereof. In an exemplaryembodiment, this method may be used to produce a thin, flexible andstackable PDLC material 1 having a thickness of about 3-30 μm, morepreferably, about 3-10 μm and most preferably, about 5 μm.

In another embodiment, the PDLC may be a block co-polymer dispersedliquid crystal (BCP) system. The BCP system may be self-assembled in thesame manner as the self-assembling PDLC. During polymerization, monomersof the PDLC mixture further react to forms block copolymer structures 8which are dispersed in the PDLC matrix. Thus, the block copolymerstructures 8 may be used to drive formation of a particular structurewithin the polymer matrix. As shown in FIGS. 3( a)-3(b), blockco-polymer 8 dispersed in the PDLC matrix may have a wire structure. Theresulting BCP system, therefore, may be fabricated with a highlystructured morphology that enhances solar energy conversion efficiencyby, for example, using the block copolymer structure to integrate in thepolymer matrix, a structure that may enhance electrical conduction inthe polymer matrix and/or to facilitate and/or guide electricaltransport in a particular direction. In an exemplary embodiment, the BCPsystem may be a bottom-up self-assembling hexagonally packed conductiveblock co-polymer formed from a liquid crystal substrate. Conductiveelements 4 may be either self-assembled or may be incorporated before,during or after polymerization.

In general, the various different embodiments of the PDLC photovoltaicdevice of the present invention overcome the inefficiencies and limitedapplications of the prior art. The highly structured morphology of thepresent invention enhances solar energy conversion efficiency as well aselectrical current output. Additionally, because PDLC material 1 may beoptically transparent, flexible, durable, and have any geometricconfiguration or a combination thereof, the PDLC photovoltaic device ofthe present invention may be more adaptable to a wide variety ofapplications in comparison to conventional solar cells. Furthermore, thePDLC photovoltaic device of the present invention is inexpensive andeasy to manufacture. In particular, no external energy is required formanufacturing the self-assembling embodiments. The device may also beenvironmentally friendly because it is fabricated from organicmaterials; unlike the devices of the prior art, the present inventiondoes not require any rare-earth compounds.

The photovoltaic device of the present invention may be used for a widevariety of applications in the fields of alternative energy generation,particularly nano-photonics alternative energy generation. The variousnovel material properties of the PDLC photovoltaic device enable thecustomization of the photovoltaic device for different applications. Forexample, a flexible PDLC photovoltaic device allows for the creation ofcurved and other multi-plane panels. Such panels may be used to conformto any curved or other multi-planar structures, such as the curvedfaçade of a modern building or a curved surface of an electronic devicesuch as a cell phone case.

Optical transparency enables the use of the PDLC photovoltaic device onor in clear surfaces, such as windows panes, and allows for theinvention to be applied to the surface of any structure or product as apaint or coating mixture. In one example, the transparent and flexiblethin PDLC films may be laminated onto windows and product surfaces.Transparency of the PDLC material 1 allows the photovoltaic device to beat least substantially invisible and therefore does not have an adverseaesthetic impact. In an exemplary embodiment, the invention may bepotentially useful for applications including printable circuitry,flexible displays, paints such as road paints, vehicle paints and housepaints, and optical communications.

EXAMPLES

A number of preliminary PDLC formulations have been created and tested.Nematic liquid crystalline material was employed in PEDOT:PSS. Filmsthat have thicknesses between 50 nm and 2 μm were created. The filmswere examined using a four point probe, optical profilometer, andscanning electron microscope. Shown below are three formulations whichexhibit good conductivity and dispersion of liquid crystal in thepolymer.

TABLE 1 (All Values in Terms of Weight Fraction) Darocur Tween DimethylPEDOT:PSS/ E7 250 20 Sulfoxide Formu- Water Dispersion (liquid (photo-(surfac- (for added lation (polymer) crystal) initiator) tant)conductivity) 1 0.9060 0.0039 0 0 0.0910 2 0.8969 0.0035 0.0099 0 0.08973 0.8969 0.0035 0 0.0099 0.0897Using a surfactant, a material layer was created in between the liquidcrystal droplets and polymer, which may be useful to tune theformulation properties.

The formula for Tween 20 surfactant used in the examples is as follows:

The formula for PEDOT:PSS used in the examples is as follows:

The foregoing examples have been presented for the purpose ofillustration and description and are not to be construed as limiting thescope of the invention in any way. The scope of the invention is to bedetermined from the claims appended hereto.

1. A photovoltaic device comprising: a polymer dispersed liquid crystalmaterial comprising: a conductive polymer; conductive elements dispersedon said conductive polymer; and conductive elements dispersed on asurface of said conductive polymer and within said conductive polymer ina manner whereby said polymer dispersed liquid crystal material compriseat least a central region which does not contain said conductiveelements. light absorbing liquid crystals dispersed in said conductivepolymer, wherein said polymer dispersed liquid crystal material iscapable of generating electrical energy when exposed to radiation; andat least one electric lead operatively associated with at least one ofsaid conductive elements of said polymer dispersed liquid crystalmaterial for conducting generated electrical energy.
 2. The device ofclaim 1, wherein said conductive polymer is selected from the groupconsisting of: PEDOT:PSS, polyaniline and mixtures thereof.
 3. Thedevice of claim 1, wherein said conductive elements comprise at leastone of metallic nanoparticles and water-complexed metallicnanoparticles.
 4. The device of claim 43, wherein said metallicnanoparticles comprise at least one of silver, indium, tin, tin oxide,zinc, zinc oxide, silicon, lead and copper.
 5. The device of claim 1,wherein said liquid crystals comprise discotic liquid crystals.
 6. Thedevice of claim 5, wherein said liquid crystals further comprise nematicliquid crystals, chiral nematic liquid crystals and combinationsthereof.
 7. The device of claim 1, wherein said polymer dispersed liquidcrystal material is flexible.
 8. The device of claim 1, wherein saidradiation is selected from the group consisting of near infraredradiation, ultraviolet radiation, visible radiation and combinationsthereof.
 9. The device of claim 1, wherein said polymer dispersed liquid1 crystal material has a solar energy conversion efficiency of greaterthan 3%.
 10. The device of claim 1, further comprising a container forretaining said polymer dispersed liquid crystal material, and whereinsaid container comprises electrically conductive elements.
 11. Thedevice of claim 1, wherein said liquid crystals are randomly dispersedthroughout said conductive polymer.
 12. The device of claim 1, whereinsaid liquid crystals are dispersed in said conductive polymer accordingto a holographic pattern.
 13. The device of claim 1, wherein saidconductive polymer further comprises block co-polymers. 14-18.(canceled)
 19. A photovoltaic device comprising: a photo-curable polymerdispersed liquid crystal material comprising: a conductive polymer;light absorbing liquid crystals dispersed in said conductive polymer,and conductive elements dispersed on a surface of said conductivepolymer and within said conductive polymer in a manner whereby saidpolymer dispersed liquid crystal material comprise at least a centralregion which does not contain said conductive elements. wherein saidpolymer dispersed liquid crystal material is capable of generatingelectrical energy when exposed to radiation; and a container forretaining said polymer dispersed liquid crystal material, wherein saidcontainer comprises electrically conductive elements; and an electriclead for conducting electrical energy operatively associated with saidconductive elements of said polymer dispersed liquid crystal materialand said electrically conductive elements of said container.
 20. Thedevice of claim 20, wherein said polymer dispersed liquid crystalmaterial is transparent and flexible.
 21. The device of claim 1, whereinsaid conductive elements form both an anode and a cathode of saiddevice.
 22. The device of claim 19, wherein said conductive elementsform both an anode and a cathode of said device.